1. Field of the Invention
The present invention relates to a television meeting unit, a television meeting system, and a method for controlling a television meeting system, and particularly relates to a television meeting unit, a television meeting system, and a method for controlling a television meeting system capable of shortening the time required to display a picture of meeting participants to a new participant who participates in the middle of a meeting.
2. Description of Prior Art
Heretofore, a unit for multiplying the picture and voice at multiple points, namely so-called MCU (Multipoint Control Unit), is needed to hold a television meeting between multiple points.
However, with development of the Internet recently, the group broadcast function so-called multicast has been available, and as the result it becomes possible by use of the multicast to hold an electronic meeting between multiple points without preparation of a particular unit such as MCU.
FIG. 1 and FIG. 2 show a typical exemplary structure of a multicast television meeting system that uses the picture and voice. FIG. 1 shows a connection diagram to a network, and FIG. 2 is a functional block diagram for showing a schematic structure of terminal unit. The picture and voice generated from the respective terminal units 12-1 to 12-x are transmitted broadcasterly to the respective terminal units 12-1 to 12x, and the received picture and voice are displayed individually or in the synthesized form to realize the television meeting.
The picture and voice of a television meeting system in the form of compressed code are transmitted usually because of the communication capacity restriction. Typically, H. 261 format or MPEG1 format is used as the picture compression coding system. In these picture compression coding systems, the in-frame coded picture in which the pixel value is coded as it is and the inter-frame prediction coded picture are used with switching selectively. The time redundancy of the picture with slight motion and change is reduced by use of the inter-frame prediction coded picture in which the difference between the previous frame and the next frame is coded because the next frame is very similar to the previous frame. On the other hand, in the case of the picture with quick motion or scene change, the in-frame coded picture is used effectively in which the pixel value is coded as it is used effectively because the correlation between frames is slight. In the general television meeting, the in-frame coded picture is transmitted at first and then the inter-frame coded picture is transmitted thereafter because the motion is not so quick.
At first in the case that a participant terminal participates in the middle in the conventional multicast meeting unit, the new participant receives the inter-frame prediction coded picture that is the meeting data served up to that time. Therefore, the terminal that participates in the middle and receives the inter-frame prediction coded picture cannot display a normal picture because no reference picture (in-frame coded picture) is available, or cannot display the picture until it receives an in-frame coded picture.
At second in the case that the processing capability of the new participant terminal is different, it is required for every participant terminal to perform with a set value within the processable range and furthermore it is required to change the set value due to the middle participation.
To solve the above-mentioned problem, the present invention is provided with a function that a middle participation information is transmitted when a terminal (middle participation terminal) participates in a meeting in the middle, and other terminals (already participating terminal) receive and detect the information and transmit the in-frame coded picture (I-frame) instead of the inter-frame prediction coded picture when the already participating terminals transmit the data. Thereby, it becomes possible to display a picture smoothly (a picture of a meeting can be displayed in a short time) to the terminal that participates in the middle and the multiple point television meeting is held smoothly by use of a multicast meeting unit.
Furthermore, the present invention is provided with a function that the processing capability information on terminals that are participating in a meeting and terminals that are to participate in the meeting is held, collated, and converted to the coded parameter that is processable by any terminal. Thereby, the information is converted so as to be processable by any terminal in the case that it is required to convert the coding parameter due to the middle participation.
Furthermore, the present invention is provided with a function that the priority adding function to terminals that precipitate in a meeting and terminals that are to participate in the meeting, and the coding parameter of the important data is converted. Thereby, the individual terminals are coded correspondingly to the priority, and the important subject is discussed preferentially in the meeting.
Furthermore, the present invention is provided with a function that the priority of the terminals are managed so as to avoid the band over due to I-frame broadcast transmission by adjusting the middle participation and the terminal performance difference to transmit I-frame from the terminal of the higher priority. Thereby, a picture of the terminal of the higher priority is displayed first, and the picture of other meeting participants is displayed later, and as the result a picture of the terminal of higher priority can be displayed earlier without adverse effect on the band of the network.
Therefore, the first object of the present invention is to shorten the time for waiting the display of a picture received by the middle participation terminal in a multicast meeting unit.
The second object of the present invention is to make the coding parameter acceptable to every terminal even in the case that the coding parameter, which has been used by every terminal, becomes unacceptable to a part of terminals due to the middle participation in the meeting.
The above-mentioned objects and advantages of the present invention will be apparent based on the embodiments described in detail hereinafter with reference to the drawings.